U.S. patent number 8,392,922 [Application Number 12/719,700] was granted by the patent office on 2013-03-05 for marshaling results of nested tasks.
This patent grant is currently assigned to Microsoft Corporation. The grantee listed for this patent is John J. Duffy, Joseph E. Hoag, Danny S. Shih, Stephen H. Toub. Invention is credited to John J. Duffy, Joseph E. Hoag, Danny S. Shih, Stephen H. Toub.
United States Patent |
8,392,922 |
Toub , et al. |
March 5, 2013 |
Marshaling results of nested tasks
Abstract
The present invention extends to methods, systems, and computer
program products for marshaling results of nested tasks. Unwrap
methods are used to reduce the level of task nesting and insure
that appropriate results are marshaled between tasks. A proxy task
is used to represent the aggregate asynchronous operation of a
wrapping task and a wrapped task. The proxy task has a completion
state that is at least indicative of the completion state of the
aggregate asynchronous operation. The completion state of the
aggregate asynchronous operation is determined and set from one or
more of the completion state of the wrapping task and the wrapped
task. The completion state of the proxy task can be conveyed to
calling logic to indicate the completion state of the aggregate
asynchronous operation to the calling logic.
Inventors: |
Toub; Stephen H. (Seattle,
WA), Hoag; Joseph E. (Bothell, WA), Duffy; John J.
(Seattle, WA), Shih; Danny S. (Seattle, WA) |
Applicant: |
Name |
City |
State |
Country |
Type |
Toub; Stephen H.
Hoag; Joseph E.
Duffy; John J.
Shih; Danny S. |
Seattle
Bothell
Seattle
Seattle |
WA
WA
WA
WA |
US
US
US
US |
|
|
Assignee: |
Microsoft Corporation (Redmond,
WA)
|
Family
ID: |
44532390 |
Appl.
No.: |
12/719,700 |
Filed: |
March 8, 2010 |
Prior Publication Data
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|
|
Document
Identifier |
Publication Date |
|
US 20110219380 A1 |
Sep 8, 2011 |
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Current U.S.
Class: |
718/101; 718/102;
718/103 |
Current CPC
Class: |
G06F
9/46 (20130101) |
Current International
Class: |
G06F
9/46 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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WO 2009041801 |
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Apr 2009 |
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WO |
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Other References
Albahari, Joe, "AggregateException with a simple Future . . .
why?", Parallel Computing, Apr. 20, 2009, 8 pages, found at
/social.msdn.microsoft.com/Forums/en-US/parallelextensions/thread/3786be5-
a-0381-4a18-b8e5-c66f5a8c3bf7. cited by applicant .
Whetstone, James, "How to marshal complex data structures", Feb. 4,
2007, 28 pages, found at
eggheadcafe.com/software/aspnet/29183161/how-to-marshal-complex-da.aspx.
cited by applicant .
Grabmuller, Martin, Monad Transformers Step by Step, Oct. 16, 2006,
13 pages. cited by applicant .
Erwig, Martin, "Monadification of Functional Programs", School of
EECS, Oregon State University, Corvallis, OR, Feb. 27, 2004, 34
pages. cited by applicant .
Fischer, Sebastian, et al., "Reinventing Haskell Backtracking",
Christina-Albrechts University of Kiel, Germany, Based on
information and belief available, at least as early as Nov. 24,
2009, 14 pages. cited by applicant.
|
Primary Examiner: Truong; Camquy
Attorney, Agent or Firm: Workman Nydegger
Claims
What is claimed:
1. At a computer system including one or more processors and system
memory, a computer-implemented method for marshaling the state of
one task to another task, the computer-implemented method
comprising: an act of receiving a call to a wrapping task from
calling logic, the wrapping task having a result that is
represented by a wrapped task wrapped within the wrapping task; an
act of receiving at an unwrap component an extension call to the
wrapping task and creating a proxy task; an act of returning the
proxy task from the unwrap component to the calling logic, the
proxy task returned to the calling logic without requiring the
calling logic to wait for completion of either the wrapping task or
the wrapped task; an act of determining at a completion state
determination component of the unwrap component the completion
state of the proxy task, the proxy task having a completion state
that is determined by at least the completion state of the wrapped
task when the completion state of the wrapping task indicates that
the wrapping task ran to completion, and if the wrapped task is
null then setting the state of the proxy to a canceled state
otherwise the state of the proxy being determined from the
completion state that is determined for the wrapped task; an act of
setting the completion state of the proxy task based on the
completion state determined by the completion state determination
component; and an act of conveying from the unwrap component the
completion state of the proxy task to the calling logic.
2. The method as recited in claim 1, wherein the act of determining
the completion state of the proxy task is based on the wrapping
task and the wrapped task both being ran to completion.
3. The method as recited in claim 2, wherein the completion state
of the proxy task represents an aggregate asynchronous operation
ran to completion.
4. The method as recited in claim 2, further comprising an act of
yielding result data from the wrapped task to the proxy task.
5. The method as recited in claim 4, wherein the act of conveying
the completion state of the proxy task to the calling logic
comprises an act of conveying the wrapped task's result data along
with the completion status of the proxy task to the calling
logic.
6. The method as recited in claim 1, wherein the act of determining
the completion state of the proxy task is based on one of the
wrapping task and the wrapped task being canceled by an external
action that caused the one of the wrapping task and the wrapped
task to cease operation.
7. The method as recited in claim 1, wherein determining the
completion state of the proxy task comprises determining if (i) the
wrapping task is either cancelled or faulted; or (ii) the wrapping
task ran to completion such that the wrapped task is either
cancelled, faulted or ran to completion.
8. The method as recited in claim 1, wherein the act of determining
the completion state of the proxy task is based on an internal
fault in one of the wrapping task and the wrapped task thereby
causing the one of the wrapping task and the wrapped task to cease
operation.
9. The method as recited in claim 8, further comprising an act of
generating exception data corresponding to the internal fault of
the one of the wrapping task and the wrapped task.
10. The method as recited in claim 9, wherein the act of returning
the completion state of the proxy task to the calling logic
comprises an act of returning the exception data along with the
completion status of the proxy task to the calling logic.
11. The method as recited in claim 1, wherein if the wrapping task
does not run to completion, then determining the completion status
of the proxy task is based on the completion status of the wrapping
task.
12. The method as recited in claim 1, wherein the act of receiving
call to a wrapping task from calling logic comprises an act of
receiving a call to a task of the format Task<Task>; and
wherein the act of returning the completion state of the proxy task
to the calling logic comprises an act of returning the completion
state of a representative task of the format Task.
13. The method as recited in claim 1, wherein the act of receiving
a call to a wrapping task from the calling logic comprises an act
of receiving a call to a task of the format
Task<Task<TResult>>; and wherein the act of returning
the completion state of the proxy task to the calling logic
comprises an act of returning the completion state of a
representative task of the format Task<TResult>.
14. A computer program product for use at a computer system, the
computer program product for implementing at one or more processors
a method for marshaling the state of one task to another task, the
computer program product comprising one or more computer storage
media having stored thereon computer-executable instructions that,
when executed at the one or more processors, cause the computer
system to perform the method, including the following: receive a
call to a wrapping task from calling logic, the wrapping task
having a result that is represented by a wrapped task wrapped
within the wrapping task; receive at an unwrap component an
extension call to the wrapping task and creating a proxy task;
return the proxy task from the unwrap component to the calling
logic, the proxy task returned to the calling logic without
requiring the calling logic to wait for completion of either the
wrapping task or the wrapped task; determine at a completion state
determination component of the unwrap component the completion
state of the proxy task, the proxy task having a completion state
that is determined by at least the completion state of the wrapped
task when the completion state of the wrapping task indicates that
the wrapping task ran to completion, and if the wrapped task is
null then setting the state of the proxy to a canceled state
otherwise the state of the proxy being determined from the
completion state that is determined for the wrapped task; set the
completion state of the proxy task based on the completion state
determined by the completion state determination component; and
convey from the unwrap component the completion state of the proxy
task to the calling logic.
15. The computer program product as recited in claim 14, wherein
the completion state of the proxy task represents an aggregate
asynchronous operation for both the wrapping task and the wrapped
task.
16. The computer program product as recited in claim 15, wherein
determining the completion state of the proxy task comprises
determining if (i) the wrapping task is either cancelled or
faulted; or (ii) the wrapping task ran to completion such that the
wrapped task is either cancelled, faulted or ran to completion.
17. The computer program product as recited in claim 14, wherein
the method further comprising yielding result data from the wrapped
task to the proxy task, and wherein conveying the completion state
of the proxy task to the calling logic comprises an act of
conveying the wrapped task's result data along with the completion
status of the proxy task to the calling logic.
18. The computer program product as recited in claim 14, wherein
receiving a call to a wrapping task from the calling logic
comprises receiving a call to a wrapping task having a format
selected from among: Task<TResult> and
Task<Task<TResult>>.
19. The computer program product as recited in claim 14, wherein if
the wrapping task does not run to completion, then determining the
completion status of the proxy task is based on the completion
status of the wrapping task.
20. A computer system, the computer system including: system
memory; one or more processors; and one or more computer storage
media having stored thereon computer-executable instructions
representing calling logic, a wrapping task, and an unwrap
component, wherein the wrapping task further wraps a wrapped task,
the calling logic being configured to: call the wrapping task;
receive a handle to a proxy task from the unwrap component; receive
a completion state of the proxy task, the completion state of the
proxy task indicating the completion state of an aggregate
asynchronous operation representing the wrapping task and the
wrapped; the unwrap component further including a wrapping task
state determination component, wrapped task state determination
component, a completion state determination component, and a null
checker, wherein the unwrap component is configured to: receiving
the wrapping task; create the proxy task; return the handle to
proxy task to the calling logic, the proxy task returned to the
calling logic without requiring the calling logic to wait for
completion of either the wrapping task or the wrapped task;
determine the completion state of the aggregate asynchronous
operation, including: the wrapping task state determination
component determining the completion state of the wrapping task;
the null checker determining if the wrapped task is not NULL; and
the wrapped task state determination component determining the
completion state of the wrapped task when the completion state of
the wrapping task indicates that the wrapping task ran to
completion and the wrapped task is not NULL; the completion state
determination component setting the completion state of the proxy
task to one of: a) the completion state of the wrapped task when
the completion state of the wrapping task indicates that the
wrapping task ran to completion or b) the completion state of the
wrapping task when the completion state of the wrapping task
indicates that the wrapping task did not run to completion; and the
completion state determination component conveying the completion
state of the proxy task to the calling logic to at least indicate
the completion state of the aggregate asynchronous operation to the
calling logic.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
Not Applicable.
BACKGROUND
Background and Relevant Art
Computer systems and related technology affect many aspects of
society. Indeed, the computer system's ability to process
information has transformed the way we live and work. Computer
systems now commonly perform a host of tasks (e.g., word
processing, scheduling, accounting, etc.) that prior to the advent
of the computer system were performed manually. More recently,
computer systems have been coupled to one another and to other
electronic devices to form both wired and wireless computer
networks over which the computer systems and other electronic
devices can transfer electronic data. Accordingly, the performance
of many computing tasks are distributed across a number of
different computer systems and/or a number of different computing
environments.
In some computing environments, a task is more specifically defined
as a work item that represents an operation an application is to
perform. Many tasks are configured to return a value of a
particular type (e.g., integer, string, etc.) to pass information
back to an application that performed the task. For example,
Task<TResult> is a task whose operation returns a value of
type TResult. It is also not uncommon for tasks to be nested within
one another. When tasks are nested, the return value type for a
task (the outer task) may be another task (the inner task). For
example, Task<Task> is task whose operation returns a value
of type Task. A nested task can also be configured to return a
further value. For example, Task<Task<TResult>> is task
whose operation returns a value of type Task<TResult> (which
is, in turn, configured to return a value of type TResult).
A variety of different computing scenarios can produce nested
tasks. Unfortunately, nested tasks can lead to unexpected
application behaviors (e.g., bugs) that are easily overlooked
and/or difficult to correct.
For example, when an (outer) task is called, the (outer) task can
call a further (inner) task to create desired results for the task.
However, if the further (inner) task is to take some time to
complete, in may be desirable to have the further (inner) task
complete asynchronously so that the (outer) task does not block
waiting for a result.
For example, consider an outer task that returns an integer count
of the number of friends on a person's friends list. The outer task
can be of the form Task<int>. Within the outer task can be an
asynchronous call to a network database that stores the friends
list. Since the call to the network database is asynchronous, the
outer task does not block and its thread is released. However, the
outer task must still return a value, even though it completes
before the network database call and thus does not have the count
of the number of friends. Thus, the outer task returns an inner
task that represents the completion of the database call, which is
also of the form Task<int>. As such, the outer task is
essentially represented as a Task<Task<int>>.
Accordingly, accessing the outer task's results returns the inner
task (i.e., Task<int>), which is a reference to the item that
is going to return the count of the number of friends.
As the number of asynchronous tasks increases, so does the
potential for unexpected application behavior. For example, an API
can include functionality for asynchronously logging into a Web
service (e.g., a social networking site), retrieving a list of
friends, and sending an electronic mail to each friend. A LogOn
method takes a username and password, and it returns a
Task<TResult> that represents the log on operation. When the
log on operation is complete, the Task's Result will be a
UserToken. For example:
public Task<UserToken> LogOn(string username, string
password);
A GetFriendsList method takes a UserToken, and it returns a
Task<TResult> that represents the friend list retrieval
operation. When the friend list retrieval operation is complete,
the Task's Result will be a FriendCollection. For example:
public Task<FriendCollection> GetFriendList(UserToken
userToken);
A SendMail method takes a Friend, and it returns a Task that
represents the email sending operation. For example:
public Task SendEmail(Friend friend, string subject, string
body);
A user may desire to write code utilizing these APIs and task
continuations, which are used to schedule a task when the original
has completed. For example:
TABLE-US-00001 1. var userToken = LogOn(user, pass); 2. var friends
= userToken.ContinueWith(.sub.-- =>
GetFriendList(userToken.Result)); 3. var emails =
friends.ContinueWith(.sub.-- => 4. { 5. var sentMails = new
List<Task>( ); 6. foreach(var friend in friends.Result) 7. {
8. sentMails.Add(SendEmail(friend, subject, body)); 9. } 10. return
Task.Factory.ContinueWhenAll( 11. sentMails.ToArray( ), tasks =>
Task.WaitAll(tasks)); 12. }); 13. emails.ContinueWith(.sub.-- =>
Console.WriteLine("All emails sent"));
Although a ".ContinueWith" is included at line 2, this indicates
that the code is to continue when the outer task completes. Thus,
when the LogOn operation has asynchronously completed, the call to
GetFriendList in line 2 will be invoked to asynchronously retrieve
the friends list. This call will return a
Task<FriendCollection> to represent the result of the
asynchronous operation. Because the code in the delegate passed to
ContinueWith at line 2 returns a Task<FriendCollection>, the
`friends` variable is Task<Task<FriendCollection>>. The
friends' variable being Task<Task<FriendCollection>>
causes a compiler error at the foreach loop, because
`friends.Result` returns a Task<FriendCollection> instead of
a FriendCollection. Other similar problems occur at other lines in
the code sample.
These and other similar types of compiler errors can often be
solved by avoiding type inference (i.e., not using the `var`
keyword). However, even when a developer realizes the type
mismatch, additional logic must still be coded to unwrap the
`friends` Task so that it returns an actual FriendCollection.
Coding such logic is nontrivial and can be relatively difficult if
the logic is to account for exceptions, cancellation, etc.
BRIEF SUMMARY
The present invention extends to methods, systems, and computer
program products for marshaling results of nested tasks. For
example, embodiments of the invention facilitate marshaling the
state of one task to another task. A call to a wrapping task is
received from calling logic. The wrapping task has a result that is
represented by a wrapped task wrapped within the wrapping task.
A proxy task that represents the aggregate asynchronous operation
of the wrapping task and the wrapped task is created. The proxy
task has a completion state that is at least indicative of the
completion state of the aggregate asynchronous operation. The proxy
task is returned to the calling logic without requiring the calling
logic to wait for completion of either the wrapping task or the
wrapped task.
The completion state of the aggregate asynchronous operation is
determined. Determining the completion state of the aggregate
asynchronous operation includes determining the completion state of
the wrapping task. When the completion state of the wrapping task
indicates that the wrapping task ran to completion, determining the
completion state of the aggregate asynchronous operation also
includes determining the completion state of the wrapped task.
The completion state of the proxy task is set to the completion
state of the wrapped task when the completion state of the wrapping
task indicates that the wrapping task ran to completion.
Alternately, completion state of proxy task is set to the
completion state of the wrapping task when the completion state of
the wrapping task indicates that the wrapping task did not run to
completion. Upon completion of the aggregate asynchronous
operation, the completion state of the proxy task is conveyed to
the calling logic to at least indicate the completion state of the
aggregate asynchronous operation to the calling logic.
This summary is provided to introduce a selection of concepts in a
simplified form that are further described below in the Detailed
Description. This Summary is not intended to identify key features
or essential features of the claimed subject matter, nor is it
intended to be used as an aid in determining the scope of the
claimed subject matter.
Additional features and advantages of the invention will be set
forth in the description which follows, and in part will be obvious
from the description, or may be learned by the practice of the
invention. The features and advantages of the invention may be
realized and obtained by means of the instruments and combinations
particularly pointed out in the appended claims. These and other
features of the present invention will become more fully apparent
from the following description and appended claims, or may be
learned by the practice of the invention as set forth
hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS
In order to describe the manner in which the above-recited and
other advantages and features of the invention can be obtained, a
more particular description of the invention briefly described
above will be rendered by reference to specific embodiments thereof
which are illustrated in the appended drawings. Understanding that
these drawings depict only typical embodiments of the invention and
are not therefore to be considered to be limiting of its scope, the
invention will be described and explained with additional
specificity and detail through the use of the accompanying drawings
in which:
FIG. 1A illustrates an example computer architecture that
facilitates marshaling the state of one task to another task.
FIG. 1B illustrates a more detailed view of the unwrap component
from FIG. 1A
FIG. 2 illustrates a flow chart of an example method for marshaling
the state of one task to another task.
FIGS. 3A and 3B illustrate examples of unwrapping a task.
DETAILED DESCRIPTION
The present invention extends to methods, systems, and computer
program products for marshaling results of nested tasks. For
example, embodiments of the invention facilitate marshaling the
state of one task to another task. A call to a wrapping task is
received from calling logic. The wrapping task has a result that is
represented by a wrapped task wrapped within the wrapping task.
A proxy task that represents the aggregate asynchronous operation
of the wrapping task and the wrapped task is created. The proxy
task has a completion state that is at least indicative of the
completion state of the aggregate asynchronous operation. In
general, a completion state for a task, including any of the
wrapping task, wrapped task, and proxy task, can be one of: ran to
completion with results data, faulted with exception data, or was
canceled. However, other completion states are also possible. The
proxy task is returned to the calling logic without requiring the
calling logic to wait for completion of either the wrapping task or
the wrapped task.
The completion state of the aggregate asynchronous operation is
determined. Determining the completion state of the aggregate
asynchronous operation includes determining the completion state of
the wrapping task. When the completion state of the wrapping task
indicates that the wrapping task ran to completion, determining the
completion state of the aggregate asynchronous operation also
includes determining the completion state of the wrapped task.
The completion state of the proxy task is set to the completion
state of the wrapped task when the completion state of the wrapping
task indicates that the wrapping task ran to completion.
Alternately, completion state of proxy task is set to the
completion state of the wrapping task when the completion state of
the wrapping task indicates that the wrapping task did not run to
completion. Upon completion of the aggregate asynchronous
operation, the completion state of the proxy task is conveyed to
the calling logic to at least indicate the completion state of the
aggregate asynchronous operation to the calling logic.
Embodiments of the present invention may comprise or utilize a
special purpose or general-purpose computer including computer
hardware, such as, for example, one or more processors and system
memory, as discussed in greater detail below. Embodiments within
the scope of the present invention also include physical and other
computer-readable media for carrying or storing computer-executable
instructions and/or data structures. Such computer-readable media
can be any available media that can be accessed by a general
purpose or special purpose computer system. Computer-readable media
that store computer-executable instructions are physical storage
media. Computer-readable media that carry computer-executable
instructions are transmission media. Thus, by way of example, and
not limitation, embodiments of the invention can comprise at least
two distinctly different kinds of computer-readable media: computer
storage media and transmission media.
Computer storage media includes RAM, ROM, EEPROM, CD-ROM or other
optical disk storage, magnetic disk storage or other magnetic
storage devices, or any other medium which can be used to store
desired program code means in the form of computer-executable
instructions or data structures and which can be accessed by a
general purpose or special purpose computer.
A "network" is defined as one or more data links that enable the
transport of electronic data between computer systems and/or
modules and/or other electronic devices. When information is
transferred or provided over a network or another communications
connection (either hardwired, wireless, or a combination of
hardwired or wireless) to a computer, the computer properly views
the connection as a transmission medium. Transmissions media can
include a network and/or data links which can be used to carry or
desired program code means in the form of computer-executable
instructions or data structures and which can be accessed by a
general purpose or special purpose computer. Combinations of the
above should also be included within the scope of computer-readable
media.
Further, upon reaching various computer system components, program
code means in the form of computer-executable instructions or data
structures can be transferred automatically from transmission media
to computer storage media (or vice versa). For example,
computer-executable instructions or data structures received over a
network or data link can be buffered in RAM within a network
interface module (e.g., a "NIC"), and then eventually transferred
to computer system RAM and/or to less volatile computer storage
media at a computer system. Thus, it should be understood that
computer storage media can be included in computer system
components that also (or even primarily) utilize transmission
media.
Computer-executable instructions comprise, for example,
instructions and data which, when executed at a processor, cause a
general purpose computer, special purpose computer, or special
purpose processing device to perform a certain function or group of
functions. The computer executable instructions may be, for
example, binaries, intermediate format instructions such as
assembly language, or even source code. Although the subject matter
has been described in language specific to structural features
and/or methodological acts, it is to be understood that the subject
matter defined in the appended claims is not necessarily limited to
the described features or acts described above. Rather, the
described features and acts are disclosed as example forms of
implementing the claims.
Those skilled in the art will appreciate that the invention may be
practiced in network computing environments with many types of
computer system configurations, including, personal computers,
desktop computers, laptop computers, message processors, hand-held
devices, multi-processor systems, microprocessor-based or
programmable consumer electronics, network PCs, minicomputers,
mainframe computers, mobile telephones, PDAs, pagers, routers,
switches, and the like. The invention may also be practiced in
distributed system environments where local and remote computer
systems, which are linked (either by hardwired data links, wireless
data links, or by a combination of hardwired and wireless data
links) through a network, both perform tasks. In a distributed
system environment, program modules may be located in both local
and remote memory storage devices.
FIG. 1A illustrates an example computer architecture 100 that
facilitates marshaling the state of one task to another task.
Referring to FIG. 1A, computer architecture 100 includes calling
logic 133, wrapping task 111, and unwrap component 101. Wrapping
task 111 further includes wrapped task 112. Each of the components
depicted in computer architecture 100 can be connected to one
another via a computer system bus. Accordingly, the components can
communicate with one another over the computer system bus.
Alternately, one or more of the depicted components in computer
architecture 100 can be connected to one another over (or be part
of) a network, such as, for example, a Local Area Network ("LAN"),
a Wide Area Network ("WAN"), and even the Internet. Accordingly,
each of the depicted computer systems as well as any other
connected computer systems and their components, can create message
related data and exchange message related data (e.g., Internet
Protocol ("IP") datagrams and other higher layer protocols that
utilize IP datagrams, such as, Transmission Control Protocol
("TCP"), Hypertext Transfer Protocol ("HTTP"), Simple Mail Transfer
Protocol ("SMTP"), etc.) over the network.
FIG. 2 illustrates a flow chart of an example method 200 for
marshaling the state of one task to another task. Method 200 will
be described with respect to the components and data of computer
architecture 100.
Method 200 includes an act of receiving call to a wrapping task
from calling logic, the wrapping task having a result that is
represented by a wrapped task wrapped within the wrapping task (act
201). For example, wrapping task 111 can receive a call from
calling logic 133. The result of wrapping task 111 is represented
by wrapped task 112. Calling logic 133 can be another program,
executing code module, software component, etc, that desires
results from the execution of wrapping task 111.
Method 200 includes an act of creating a proxy task that represents
the aggregate asynchronous operation of the wrapping task and the
wrapped task, the proxy task having a completion state that is at
least indicative of the completion state of the aggregate
asynchronous operation (act 202). For example, during execution
wrapping task 111 can make extension call to unwrap component 101.
Unwrap component 101 can create a proxy task that represents the
aggregate asynchronous operation of the wrapping task 111 and the
wrapped task 112. The proxy task has a completion state that is at
least indicative of the completion state of the aggregate
asynchronous operation representative of wrapping task 111 and the
wrapped task 112.
Method 200 includes an act of returning the proxy task to the
calling logic, the proxy task returned to the calling logic without
requiring the calling logic to wait for completion of either the
wrapping task or the wrapped task (act 203). For example, unwrap
component 101 can return proxy task handle 132 to calling logic
133. Proxy task handle 132 can be returned to calling logic 133
without requiring calling logic 133 to wait for completion of
wrapping task 111 or wrapped task 112.
Method 200 includes an act of determining the completion state of
the aggregate asynchronous operation (act 204). For example, unwrap
component 111 can determine the completion state of the aggregate
asynchronous operation representative of wrapping task 111 and the
wrapped task 112.
FIG. 1B illustrates a more detailed view of the unwrap component
101. As depicted in FIG. 1B, unwrap component 101 includes wrapping
task state determination component 102, wrapped task state
determination component 103, completion state determination
component 104, and null checker 106. When unwrap component 101 is
called, a continuation task 113 is taken on wrapping task state
determination component 102. Wrapping task state determination
component 102 determines the completion state of the wrapping task.
The completion state of a task can include a status and optional
return data. For example, the completion state of task can be: ran
to completion (the status), ran to completion (the status) and
results data (the return data), faulted (the status) and exception
data (the return data), or canceled (the status). Other completion
states are also possible.
For example, it may be that a wrapping task is a
Task<TResult> but has a result value of null. Thus, the body
of the wrapping task did not return a Task as it was supposed to,
but instead returned a null value. When this occurs, there are
several options on how to proceed, such as faulting the proxy or
canceling the proxy.
When the state of the wrapping task is canceled or faulted with
exception data, wrapping task state determination component 102
passes the completion state of the wrapping task to completion
state determination component 104. Upon receiving the completion
state of the wrapping task, completion state determination
component 104 sets the completion state of the proxy task to the
completion state of the wrapping task. Thus, if the completion
status of wrapping task is canceled or faulted with exception data,
completion state determination component 104 correspondingly sets
the completion status of the proxy task to canceled or faulted with
exception data respectively.
On the other hand, if the state of the wrapping task ran to
completion with results data, wrapping task state determination
component 102 passes the completion state of the wrapping task to
wrapped task state determination component 103. A continuation task
121 is taken on wrapped task state determination component 103 with
the completion state of the wrapping task.
Wrapped task state determination component 103 determines the
completion state of the wrapped task. Wrapped task state
determination component 103 then passes the completion state of the
wrapped task to completion state determination component 104. Upon
receiving the completion state of the wrapped task, completion
state determination component 104 correspondingly sets the
completion status of the proxy task to completion status of the
wrapped task.
Completion state determination component 104 then outputs the
completion status of the proxy task to the calling logic.
Null checker 106 checks a wrapped task to determine if the wrapped
task is null. Detection of a null wrapped task results in a status
of canceled for the proxy task.
Thus, when the completion status of a wrapping task is canceled or
faulted, the completion state of the proxy task is set to the
completion state of the wrapping task. On the other hand, if the
completion status of a wrapping task ran to completion, the
completion state of the proxy task is set to the completion state
of the wrapped task.
Accordingly, act 204 includes an act of determining the completion
state of the wrapping task (act 205). For example, unwrap component
101 can receive wrapping task 111 containing wrapped task 112.
Continuation task 113 is taken on wrapping task state determination
component 102. Wrapping task state determination component 102
determines the completion state of wrapping task 111.
When the completion state of wrapping task 111 is canceled,
wrapping task state determination component 102 can send the
canceled state 114 to completion state determination component 104.
Similarly, when the completion state of wrapping task 111 is
faulted with exception data, wrapping task state determination
component 102 can send the faulted state 116 and exception data 117
to completion state determination component 104. On the other hand,
if the completion state of wrapping task 111 ran to completion with
results data, wrapping task state determination component 102 can
send the ran to completion state 118 and results data 119 to
wrapped task state determination component 103. Thus, wrapping task
state determination component 102 either sends the canceled or
faulted states to completion state determination component 104 or
sends the ran to completion state to wrapped task state
determination component 103.
Act 204 includes an act of determining the completion state of the
wrapped task when the completion state of the wrapping task
indicates that the wrapping task ran to completion (act 206). For
example, continuation task 121 is taken on wrapped task state
determination component 103. Wrapping task state determination
component 103 determines the completion state of wrapping task
111.
When the completion state of wrapped task 112 is canceled, wrapped
task state determination component 103 can send canceled state 122
to completion state determination component 104. Similarly, when
the completion state of wrapped task 112 is faulted with exception
data, wrapped task state determination component 103 can send
faulted state 123 and exception data 124 to completion state
determination component 104. Likewise, if the completion state of
wrapped task 112 ran to completion with results data, wrapped task
state determination component 103 can send ran to completion state
126 and results data 127 to completion state determination
component 104. Thus, when appropriate, wrapped task state
determination component 103 sends one of the canceled, faulted, or
ran to completion states to completion state determination
component 103.
Method 200 includes an act of setting the completion state of the
proxy task to one of: a) the completion state of the wrapped task
when the completion state of the wrapping task indicates that the
wrapping task ran to completion or b) the completion state of the
wrapping task when the completion state of the wrapping task
indicates that the wrapping task did not run to completion (act
207). For example, upon receiving a completion status of canceled,
faulted, or ran to completion from wrapped task state determination
component 103, completion state determination component 104 can set
the completion state of the proxy to the completion state of
wrapping task 111. On the other hand, upon receiving a completion
status of canceled or faulted from wrapping task state
determination component 102, completion state determination
component 104 can set the completion state of the proxy to the
completion state of wrapping task 111.
Generally, when the completion status of wrapping task 111 is
canceled, faulted, or ran to completion with a result of null,
wrapped task state determination component 103 is not utilized.
Method 200 includes an act of conveying the completion state of the
proxy task to the calling logic to at least indicate the completion
state of the aggregate asynchronous operation to the calling logic
(act 208). For example, unwrapping component 101 can convey
completion state 131 to calling logic 133. Completion state 131
indicates the completion state of the aggregate asynchronous
operation representing wrapping task 111 and wrapped task 112.
Some embodiments of the invention use an extension method to
transform a Task<Task> into a Task that fully represents the
original nested task, including exceptions, cancellation state,
etc. For example, FIG. 3A depicts an example of transforming a
Task<Task> into a Task. As depicted, wrapped task 303 is
wrapped inside wrapping task 302. Wrapping task 302 and wrapped
task 303 are input to unwrap component 301. Unwrap component 301
transforms wrapping task 302 and wrapped task 303 into
representative task 304. Representative task 304 fully represents
wrapped task 303.
Similarly, other embodiments of the invention use an extension
method to transform a Task<Task<TResult>> into a
Task<TResult> that fully represents the original nested task,
including exceptions, cancellation state, etc. For example, FIG. 3B
depicts an example of transforming a
Task<Task<TResult>> into a Task<TResult>. As
depicted, wrapped task 313 is wrapped inside wrapping task 312.
Wrapping task 312 and wrapped task 313 are input to unwrap
component 311. Unwrap component 311 transforms wrapping task 312
and wrapped task 313 into representative task 314. Representative
task 314 fully represents wrapped task 313.
Embodiments of the invention include using a TaskCompletionSource
<TResult> object in conjunction with a continuation Task to
marshal the completion state of one task to another. Thus, the
completion state of a nested task can be flowed to a new non-nested
task that can serve as a proxy for further computation.
Methods can be defined to implement embodiments of the invention.
The methods can be defined in virtually any programming terminology
and style, such as, for example, C++ templates, Java generics, etc.
Using C# terminology and style, methods can be defined as
follows:
TABLE-US-00002 public static Task Unwrap(this Task<Task>
task); public static Task<TResult> Unwrap<TResult>(this
Task<Task<TResult>> task);
In some embodiments, extension methods are used instead of normal
instance methods. Using extension methods helps ensure that the
Unwrap is called by objects of the appropriate type (e.g.,
Task<Task> and Task<Task<TResult>>
respectively).
The following pseudo code can be used to unwrap
Task<Task<TResult>>. Code for unwrapping
Task<Task> works in similar fashion.
TABLE-US-00003 public static Task<TResult>
Unwrap<TResult>(this Task<Task<TResult>> task) {
tcs = new TaskCompletionSource<TResult>( );
task.ContinueWith(delegate { switch (task.Status) { case
TaskStatus.RanToCompletion: if (task.Result != null) {
task.Result.ContinueWith(delegate {
tcs.SetFromTask<TResult>(task.Result); }); } else
tcs.SetCanceled( ): return; case TaskStatus.Canceled: case
TaskStatus.Faulted: tcs.SetFromTask<TResult>(task); return; }
}); return tcs.Task; }
Within the pseudo code example, a
TaskCompletionSource<TResult> is created, and its member Task
is eventually returned from the method. The returned Task is set
using continuation Task(s). First, a continuation is scheduled for
the wrapping Task. If the wrapping Task is Canceled or Faulted,
that state is marshaled to the returned Task, and the procedure is
done. If it RanToCompletion, the wrapped Task is examined. If the
wrapped Task is null, then the returned Task is canceled.
Otherwise, a continuation is scheduled for the wrapped Task to
marshal its final state (Canceled, Faulted+Exception Data, or
RanToCompletion+Result) to the returned Task.
Using unwrap extension methods can reduce unexpected program
behaviors. The following pseudo code example uses unwrap to help
insure that correct results are marshaled between tasks.
TABLE-US-00004 1. var userToken = LogOn(user, pass); 2. var friends
= userToken.ContinueWith(.sub.-- =>
GetFriendList(userToken.Result)).Unwrap( ); 3. var emails =
friends.ContinueWith(.sub.-- => 4. { 5. var sentMails = new
List<Task>( ); 6. foreach(var friend in friends.Result) 7. {
8. sentMails.Add(SendEmail(friend, subject, body)); 9. } 10. return
Task.Factory.ContinueWhenAll( 11. sentMails.ToArray( ), tasks =>
Task.WaitAll(tasks)); 12. }).Unwrap( ); 13.
emails.ContinueWith(.sub.-- => Console.WriteLine("All emails
sent"));
Within the pseudo code example, unwrap extension methods are used
at lines 2 and 12. For example, the unwrap methods at line 2
ensures that GetFriendList returns a Task<FriendCollection>
instead of a Task<Task<FriendCollection>. As such, at the
foreach loop at line 6 `friends.Result` appropriately returns a
FriendCollection (and not a Task<FriendCollection>).
Accordingly, Unwrap methods are used to reduce the level of task
nesting and ensure that appropriate results are marshaled between
tasks, for example, going from Task<Task<TResult>> to
Task<TResult> or Task<Task> to Task. Unwrap methods can
also be applied multiple times to reduce the level of multiple
nested task. For example, for
Task<Task<Task<Task>>> t, t.Unwrap( ).Unwrap(
).Unwrap( ) can be used to remove the multiple levels of nesting,
reducing the result to a Task
A proxy task is used to represent the aggregate asynchronous
operation of a wrapping task and a wrapped task. The proxy task has
a completion state that is at least indicative of the completion
state of the aggregate asynchronous operation. The completion state
of the aggregate asynchronous operation is determined and set from
one or more of the completion state of the wrapping task and the
wrapped task. The completion state of the proxy task can be
conveyed to a calling logic to indicate the completion state of the
aggregate asynchronous operation to the calling logic.
The present invention may be embodied in other specific forms
without departing from its spirit or essential characteristics. The
described embodiments are to be considered in all respects only as
illustrative and not restrictive. The scope of the invention is,
therefore, indicated by the appended claims rather than by the
foregoing description. All changes which come within the meaning
and range of equivalency of the claims are to be embraced within
their scope.
* * * * *